Tank Gun Stabilisation – Worth it or not?

V1.1 4/9/19

 

A gun stabiliser keeps a tank gun pointing in the same direction regardless of the movement of the tank carrying it. However how useful was it in real life?

General user opinion in WW2 seems to be that the stabiliser was worthless on the move but sped up the engagement a bit when stopping and firing from the halt. The following page quotes many authors which indicate that in WW2 results were mixed: https://groups.google.com/forum/#!topic/rec.games.miniatures.historical/fFzVIPpX_lQ. However UK experience reported in: Tank armament stabilisation User experience and the present situation (http://discovery.nationalarchives.gov.uk/details/r/C1824456 ) is less effusive: “Owing to the limitations inherent in the system, it was used very little operationally.”  The unspoken assumption in all this is that firing on the move without a stabiliser is completely even worthless, to the point than in WW2 the British conducted no trials I can discover in the archives. So in WW2 it was better than nothing but not much.

 

Given that the stabiliser is an expensive bit of kit the British investigated further in 1956. “Notes on the value of the stabiliser” (http://discovery.nationalarchives.gov.uk/details/r/C1824704 ) investigates how well the stabilized gun in the Centurion works from the short halt and while moving

 

As you can see from the table, the objective research flies in the face of WW2 user opinion, stabilisation makes no odds to the time spent engaging a target when firing from the short halt.

 

 

The second table compares accuracy on the move to firing halted. It’s worth noting the data was scientifically calculated rather than being based on actual firing trials.  The table requires some interpretation. Stationary tank means just that. Head on means that the firing tank is moving directly towards the target, broadside on means it is moving tangentially (moving across the target and getting no closer). As can be seen, depending on the situation, the stabiliser can be as accurate as halted fire but under some circumstances is less than a tenth as accurate. The report states “…it would seem preferable to fire on the halt if possible.”

 

So stabilisation in the Centurion as OK but not great, so surely the mighty Chieftain would be better? Let’s have a look at: Gun Control Equipment Performance of the Chieftain in Stabilised Mode (http://discovery.nationalarchives.gov.uk/details/r/C11272256 ) from 1971. I quote from the conclusions of the report, which were taken from actual trials rather than calculations: “The percentage times on a 2.3m x 2.3m target at 1000m range, excluding drift, are 21%, 9.5% and 5% at speeds of 5, 10 and 15mph.” The performance is not very impressive and quite a great deal worse than the calculated values from the Centurion.

 

It is not surprising that in: “A joint UK / FRG study of a new German concept for a future Main Battle Tank” (http://discovery.nationalarchives.gov.uk/details/r/C11161984 ) completed in 1973 it states: “firing at the short halt … is current practice in both the UK and FRG (Germany)”

 

So the Challenger comes next. Data from the Battlegroup Wargame Series 41 Vol 1 (http://discovery.nationalarchives.gov.uk/details/r/C11213389 ) from 1983 give the following chances (percentages) of a kill vs a lightly armoured APC firing from the halt. With a 120mm gun the probability of a kill should be roughly the same as the probability of a hit. Partially exposed means hull down.

 

 

This is the chart for a moving Challenger firing at the same target

 

 

Well it’s better than the Chieftain figures but still firing on the move is generally much worse than firing halted

 

One reason for stabilisation not being as accurate as halted fire is it doesn’t compensate for the firer’s motion. When firing from a moving tank you don’t actually aim at the target. Imagine aiming at a halted tank 2km away. Imagine our gun has 1000ms muzzle velocity so the shell takes two seconds to reach the target. Also imagine our tank is moving at 30kmh tangentially (across ways) to the target. When the shell leaves the gun it’s also moving at 30kmh in the direction the tank is moving. In 2s the shell travels laterally 16m. In order to hit the target you have aim 16m in front of it or the shot misses. This lead has to be calculated and applied by a harassed gunner bumping around in a moving vehicle which, as the figures indicate is somewhat challenging.  Very modern sights can compensate for this using a predictor, and the Challenger was supposed to have one, but it appears it didn’t work that well!

 

So stabilisation at least until the early 80’s is more miss than hit.